Comparison of Electrical Properties and Thermal Degradation of RGB-Organic Light Emitting Diodes

Choi, Pyungho,Park, Hyunae,Kim, Hyunwoo,Kim, Sangsoo,Choi, Byoungdeog American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.10

<P>The electrical properties and thermal degradation of red (R), green (G), and blue (B) organic-light-emitting-diodes (OLEDs) were characterized using the current-voltage (I-V) method. We investigated the temperature-dependent electrical degradation by determining the ideality factor n, series resistance r(s), and barrier height phi(B). The turn-on voltage for the R-OLED drastically decreased as temperature increased, whereas the others gradually decreased. Among the three types of OLEDs tested, the R-OLED showed the lowest current values under forward bias conditions as well as a severe temperature-dependency beyond the quasi-neutral region (QNR). The temperature-dependent variations of n and rs were largest for the R-OLED compared with the G-and B-OLEDs. This means that the R-OLED is the most easily degraded under thermal stress compared with the G-and B-OLEDs.</P>

Fabrication and Characteristics of High Mobility InSnZnO Thin Film Transistors

Choi, Pyungho,Lee, Junki,Park, Hyoungsun,Baek, Dohyun,Lee, Jaehyeong,Yi, Junsin,Kim, Sangsoo,Choi, Byoungdeog American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.5

<P>In this paper, we describe the fabrication of thin film transistors (TFTs) with amorphous indium-tin-zinc-oxide (ITZO) as the active material. A transparent ITZO channel layer was formed under an optimized oxygen partial pressure (OPP (%) = O-2/(Ar + O-2)) and subsequent annealing process. The electrical properties exhibited by this device include field-effect mobility (mu(eff)), sub-threshold swing (SS), and on/off current ratio (I-ON/OFF) values of 28.97 cm(2)/V.s, 0.2 V/decade, and 2.64 x 10(7), respectively. The average transmittance values for each OPP condition in the visible range were greater than 80%. The positive gate bias stress resulted in a positive threshold voltage (V-th) shift in the transfer curves and degraded the parameters mu(eff) and SS. These phenomena originated from electron trapping from the ITZO channel layer into the oxide/ITZO interface trap sites.</P>

Lymphomatoid papulosis after allogenic stem cell transplantation

( Sangsoo Choi ),( Sewon Hwang ),( Ji Hyun Lee ),( Young Min Park ),( Jun Young Lee ) 대한피부과학회 2015 대한피부과학회 학술발표대회집 Vol.67 No.1

Post-transplantation lymphoproliferative disorders(PTLD) are relatively common lymphoid proliferation or lymphomas that develop in a recipient of a solid organ or bone marrow allograft. Patients undergoing allogenic SCT have a PTLD incidence of about 1%. Moreover most examples are of B cell origin, and CD30+ T cell PTLDs are very rare. A 29-year-old man presented with pruritic, multiple, erythematous crusted papules on the scalp, face, trunk and both extremities which had begun about 1 week previously. He had received an allogenic peripheral blood stem cell transplantation(PBSCT) 2 weeks before his visit for acute lymphoblastic leukemia. The histopathological examination showed a wedge-shaped perivascular lymphoid infiltrate with cytologic atypia. In the immunohistochemical study, the atypical lymphocytes expressed CD30 and CD3 antigen, but not CD20, CD68, and terminal deoxy nucleotide transferase. The histopathological and clinical findings established the diagnosis of lymphomatoid papuosis(LyP). The cutaneous lesion showed progressive improvement. For newly developed multiple erythematous papules in a transplant patient, we should consider PTLD, including lymphomatoid papulosis.

Capsid integrity PCR 을 통한 공기 중 독감 및 코로나바이러스 감염력 신속 판별

최상수(Sangsoo Choi),Piri Amin,정지우(Jiwoo Jung),안상권(Sanggwon An),황정호(Jungho Hwang) 대한기계학회 2024 대한기계학회 춘추학술대회 Vol.2024 No.4

Differential coexpression analysis using microarray data and its application to human cancer

Choi, Jung Kyoon,Yu, Ungsik,Yoo, Ook Joon,Kim, Sangsoo Oxford University Press 2005 Bioinformatics Vol.21 No.24

<P><B>Motivation:</B> Microarrays have been used to identify differential expression of individual genes or cluster genes that are coexpressed over various conditions. However, alteration in coexpression relationships has not been studied. Here we introduce a model for finding differential coexpression from microarrays and test its biological validity with respect to cancer.</P><P><B>Results:</B> We collected 10 published gene expression datasets from cancers of 13 different tissues and constructed 2 distinct coexpression networks: a tumor network and normal network. Comparison of the two networks showed that cancer affected many coexpression relationships. Functional changes such as alteration in energy metabolism, promotion of cell growth and enhanced immune activity were accompanied with coexpression changes. Coregulation of collagen genes that may control invasion and metastatic spread of tumor cells was also found. Cluster analysis in the tumor network identified groups of highly interconnected genes related to ribosomal protein synthesis, the cell cycle and antigen presentation. Metallothionein expression was also found to be clustered, which may play a role in apoptosis control in tumor cells. Our results show that this model would serve as a novel method for analyzing microarrays beyond the specific implications for cancer.</P><P><B>Supplementary information:</B> Supplementary data are available at <I>Bioinformatics</I> online.</P><P><B>Contact:</B> sskimb@ssu.ac.kr</P>

An Improved Method for Charging Submicron and Nano Particles with Uniform Charging Performance

Choi, Youngjoo,Kim, Sangsoo Taylor Francis 2007 AEROSOL SCIENCE AND TECHNOLOGY Vol.41 No.3

<P> An improved method for charging submicron and nano silver particles with uniform charging performance was developed. Monodisperse silver particles were grown into microdroplets through condensation. The aerodynamic diameter and GSD of the condensed droplets were the same regardless of their original diameter. The diameter of the droplets increased from 1.7μm to 2.5 μm as the temperature of the saturator increased from 45°C to 55°C. They were charged by an indirect corona-based charger, in which the ion-generation zone is followed by a particle-charging zone through which the condensed droplets pass. The charges of the droplets were controlled by varying the droplet size, ion concentration, and strength of electric field in the charger. The solvent of the charged droplets was evaporated in an evaporator. The size distribution of the evaporated particles was measured by SMPS spectrometer and compared with their original size distribution. The particles after evaporation were slightly larger than their original particles, due to recondensation. The total charge and number concentration of the particles were measured by aerosol electrometer and CPC, to calculate the average charge. Their electrical mobility distribution was measured by SMPS spectrometer without a neutralizer, to calculate the charge distribution and average charge of the evaporated particles. The results showed the average charges of the particles were similar, regardless of initial diameter and manner of calculation. The charge distributions of the evaporated particles were identical, except for 16.9 nm particles. Ion evaporation phenomenon of particles smaller than 40 nm in diameter was not detected.</P>

Impact of Transcriptional Properties on Essentiality and Evolutionary Rate

Choi, Jung Kyoon,Kim, Sang Cheol,Seo, Jungmin,Kim, Sangsoo,Bhak, Jong The Genetics Society of America 2007 Genetics Vol.175 No.1

<P>We characterized general transcriptional activity and variability of eukaryotic genes from global expression profiles of human, mouse, rat, fly, plants, and yeast. The variability shows a higher degree of divergence between distant species, implying that it is more closely related to phenotypic evolution, than the activity. More specifically, we show that transcriptional variability should be a true indicator of evolutionary rate. If we rule out the effect of translational selection, which seems to operate only in yeast, the apparent slow evolution of highly expressed genes should be attributed to their low variability. Meanwhile, rapidly evolving genes may acquire a high level of transcriptional variability and contribute to phenotypic variations. Essentiality also seems to be correlated with the variability, not the activity. We show that indispensable or highly interactive proteins tend to be present in high abundance to maintain a low variability. Our results challenge the current theory that highly expressed genes are essential and evolve slowly. Transcriptional variability, rather than transcriptional activity, might be a common indicator of essentiality and evolutionary rate, contributing to the correlation between the two variables.</P>

CFGP 2.0: a versatile web-based platform for supporting comparative and evolutionary genomics of fungi and Oomycetes

Choi, Jaeyoung,Cheong, Kyeongchae,Jung, Kyongyong,Jeon, Jongbum,Lee, Gir-Won,Kang, Seogchan,Kim, Sangsoo,Lee, Yin-Won,Lee, Yong-Hwan Oxford University Press 2013 Nucleic acids research Vol.41 No.d1

<P>In 2007, Comparative Fungal Genomics Platform (CFGP; http://cfgp.snu.ac.kr/) was publicly open with 65 genomes corresponding to 58 fungal and Oomycete species. The CFGP provided six bioinformatics tools, including a novel tool entitled BLASTMatrix that enables search homologous genes to queries in multiple species simultaneously. CFGP also introduced Favorite, a personalized virtual space for data storage and analysis with these six tools. Since 2007, CFGP has grown to archive 283 genomes corresponding to 152 fungal and Oomycete species as well as 201 genomes that correspond to seven bacteria, 39 plants and 105 animals. In addition, the number of tools in Favorite increased to 27. The Taxonomy Browser of CFGP 2.0 allows users to interactively navigate through a large number of genomes according to their taxonomic positions. The user interface of BLASTMatrix was also improved to facilitate subsequent analyses of retrieved data. A newly developed genome browser, Seoul National University Genome Browser (SNUGB), was integrated into CFGP 2.0 to support graphical presentation of diverse genomic contexts. Based on the standardized genome warehouse of CFGP 2.0, several systematic platforms designed to support studies on selected gene families have been developed. Most of them are connected through Favorite to allow of sharing data across the platforms.</P>

Accuracy of Noninvasive Scoring Systems in Assessing Liver Fibrosis in Patients with Nonalcoholic Fatty Liver Disease: A Systematic Review and Meta-Analysis

( Sangsoo Han ),( Miyoung Choi ),( Bora Lee ),( Hye-won Lee ),( Seong Hee Kang ),( Yuri Cho ),( Sang Bong Ahn ),( Do Seon Song ),( Dae Won Jun ),( Jieun Lee ),( Jeong-ju Yoo ) 대한소화기기능성질환·운동학회 2022 Gut and Liver Vol.16 No.6

Background/Aims: Several noninvasive scoring systems have been developed to determine the risk of advanced fibrosis in nonalcoholic fatty liver disease (NAFLD). We examined the diagnostic accuracy of the fibrosis-4 (FIB-4) score and NAFLD fibrosis score (NFS) in patients with biopsy-proven NAFLD. Methods: For this meta-analysis, various databases including PubMed (MEDLINE), EMBASE, OVID Medline and the Cochrane Library were systematically searched. After the acquired abstracts were reviewed by two investigators, manuscripts were chosen for a full-text examination. Results: Thirty-six studies evaluating biopsy-proven NAFLD were selected for meta-analysis. A total of 14,992 patients were analyzed. The lower cutoff sensitivity of the FIB-4 score predicting histological fibrosis stage 3 or more (≥F3) was 69%, with specificity of 64%, positive likelihood ratio (LR+) of 1.96, and negative likelihood ratio (LR-) of 0.47. The low baseline sensitivity of the NFS score predicting ≥F3 was 70%, with a specificity of 61%, LR+ of 1.83, and LR- of 0.48. The area under the receiver operating characteristic curve (AUC) values of the FIB-4 score predicting ≥F3 and ≥F2 were 76% and 68%, respectively. The AUC values of the NFS score predicting ≥F3 and ≥F2 were 74% and 60%, respectively. Conclusions: The FIB-4 or NFS test can be used to predict the degree of liver fibrosis in NAFLD, and the diagnostic accuracy resulted as relatively high in fibrosis stages of F3 or higher. (Gut Liver 2022;16:952-963)

Hybrid Control System for Managing Voltage and Reactive Power in the JEJU Power System

Sangsoo Seo,Yun-Hyuk Choi,Sang-Gyun Kang,Byongjun Lee,Jeong-Hoon Shin,Tae-Kyun Kim 대한전기학회 2009 Journal of Electrical Engineering & Technology Vol.4 No.4

This paper proposes a hybrid voltage controller based on a hierarchical control structure for implementation in the Jeju power system. The hybrid voltage controller utilizes the coordination of various reactive power devices such as generators, switched shunt devices and LTC to regulate the pilot voltage of an area or zone. The reactive power source can be classified into two groups based on action characteristics, namely continuous and discrete. The controller, which regulates the pilot bus voltage, reflects these characteristics in the coordination of the two types of reactive power source. However, the continuous type source like generators is a more important source than the discrete type for an emergency state such as a voltage collapse, thereby requiring a more reactive power reserve of the continuous type to be utilized in the coordination in order to regulate the pilot bus voltage. Results show that the hybrid controller, when compared to conventional methods, has a considerable improvement in performance when adopted to control the pilot bus voltage of the Jeju island system.